Extraction and purification process and system of cyclohexanone-oxime

Abstract

The invention relates to an extraction and purification process of cyclohexanone-oxime, which comprises the following steps: S1, carrying out primary extraction on a cyclohexanone-oxime aqueous solution by using toluene to obtain a primary oil phase and a primary water phase, washing the primary oil phase with water to remove salt, then carrying out distillation purification, and recovering the cyclohexanone-oxime in the primary oil phase; s2, carrying out secondary extraction on the primary water phase by using methylbenzene to obtain a secondary oil phase and a secondary water phase, circulating the secondary oil phase to the primary extraction procedure, and recovering cyclohexanone-oxime in the secondary oil phase; the mass ratio of the methylbenzene used in the primary extraction to the methylbenzene used in the secondary extraction is 2: 1. According to the method disclosed by the invention, by screening the ratio of the two extraction agents, the extraction effect of the cyclohexanone-oxime in secondary extraction can be ensured under the condition of ensuring the final high purification rate of the cyclohexanone-oxime, and the loss of the cyclohexanone-oxime in a secondary extraction water phase is reduced; and meanwhile, the mass ratio of cyclohexanone oxime in the toluene oxime solution (oil phase) can be ensured to be high, so that the use amount of toluene is reduced, steam required for subsequently recovering the toluene is reduced, and the loss of the toluene can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cyclohexanone oxime refining, and in particular to a cyclohexanone oxime extraction and purification process and system. Background Art

[0002] Cyclohexanone oxime is prepared by ammonia oximation reaction. Cyclohexanone oxime and water are non-miscible systems with similar densities. It is difficult to separate them by general methods. Therefore, toluene, which is more soluble than water, is usually used to extract cyclohexanone oxime from water into toluene. The toluene solution of cyclohexanone oxime (hereinafter referred to as toluene oxime solution) is washed with water in two steps to remove inorganic salts contained therein, and then sent to the distillation system for purification. At the same time, the extracted water phase containing a small amount of cyclohexanone oxime is extracted again with toluene to purify the cyclohexanone oxime.

[0003] Conventional cyclohexanone oxime extraction and purification methods generally focus on the effect of one-time extraction and recovery of cyclohexanone oxime, and the following problems mainly exist: 1. The overall amount of toluene that needs to be added is relatively large, not less than three times the mass of cyclohexanone oxime, and the toluene loss is relatively high; 2. The amount of toluene added is proportional to the steam consumption. The more toluene is added, the more steam is consumed, and the production cost will increase; 3. The high amount of toluene added also increases the load of the extraction system, which indirectly affects the production load.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an extraction and purification process and system for cyclohexanone oxime.

[0006] The technical solution adopted by the present invention is:

[0007] In one aspect, the present invention provides an extraction and purification process for cyclohexanone oxime, comprising the following steps:

[0008] S1, extracting the cyclohexanone oxime aqueous solution once with toluene to obtain an oil phase and an aqueous phase, washing the oil phase with water to remove salt and then distilling and purifying it to recover the cyclohexanone oxime therein;

[0009] S2, extracting the primary aqueous phase with toluene for a second time to obtain a secondary oil phase and a secondary aqueous phase, and then recycling the secondary oil phase to the primary extraction step to recover cyclohexanone oxime in the secondary oil phase;

[0010] The mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 2:1.

[0011] The invention provides an extraction and purification process for cyclohexanone oxime. By screening the ratio of two extraction agents, the invention ensures a high final purification rate of cyclohexanone oxime. On the one hand, the extraction effect of cyclohexanone oxime in the secondary extraction can be ensured, and the loss of cyclohexanone oxime in the secondary extraction water phase can be reduced. On the other hand, the mass proportion of cyclohexanone oxime in the toluene oxime solution (oil phase) can be ensured to be high, thereby reducing the amount of toluene used, reducing the steam required for subsequent recovery of toluene, and reducing the loss of toluene.

[0012] Preferably, the mass of toluene used in the primary extraction is reduced to 0.4-0.8 times of the original mass, and the mass of toluene used in the secondary extraction is increased to 1.1-1.3 times of the original mass.

[0013] Preferably, the secondary extraction is countercurrent extraction.

[0014] Preferably, the conditions for the primary extraction and / or the secondary extraction are: temperature of 45-55° C. and pressure of normal pressure.

[0015] On the other hand, the present invention provides a system applied to the process described in any of the above technical solutions, comprising a heat exchanger, an extraction tank, a first pump, an extraction tower, an extraction receiving tank, and a second pump connected in sequence, wherein the feed end of the heat exchanger is used for feeding toluene and cyclohexanone oxime aqueous solution, the discharge end of the heat exchanger is connected to the middle of the extraction tank, the primary oil phase discharge end of the extraction tank is connected to the desalination and distillation purification system, the primary water phase discharge end at the bottom of the extraction tank is connected to one end of the first pump, the other end of the first pump is connected to one end of the top of the extraction tower, the other end of the top of the extraction tower is connected to the top of the extraction receiving tank as the discharge end of the secondary oil phase, the bottom of the extraction receiving tank is connected to one end of the second pump, the other end of the second pump is connected to the feed end of the heat exchanger, the secondary water phase discharge end at the bottom of the extraction tower is connected to the wastewater treatment system, and the bottom of the extraction tower is also provided with a toluene feed end. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the process structure in Example 1 of the present invention;

[0017] In the figure, 1, toluene; 2, cyclohexanone oxime aqueous solution; 3, toluene oxime solution; 4, secondary aqueous phase; 5, extraction tank; 6, heat exchanger; 7, extraction tower; 8, extraction receiving tank; 9, first pump; 10, second pump. DETAILED DESCRIPTION

[0018] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0019] An embodiment of the present invention provides an extraction and purification process for cyclohexanone oxime, comprising the following steps:

[0020] S1, extracting the cyclohexanone oxime aqueous solution once with toluene to obtain an oil phase and an aqueous phase, washing the oil phase with water to remove salt and then distilling and purifying it to recover the cyclohexanone oxime therein;

[0021] S2, extracting the primary aqueous phase with toluene for a second time to obtain a secondary oil phase and a secondary aqueous phase, and then recycling the secondary oil phase to the primary extraction step to recover cyclohexanone oxime in the secondary oil phase;

[0022] The mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 2:1.

[0023] In the conventional process of recovering cyclohexanone oxime, since the total toluene usage is usually not less than 3 times the mass of cyclohexanone oxime, when the overall toluene usage is large, the mass ratio of the toluene used in the primary extraction and the secondary extraction has no obvious effect on the total extraction effect. The inventors found that by controlling the mass ratio of toluene used in the primary extraction and the toluene used in the secondary extraction to be 2:1, under the condition that the total toluene usage is 3 times the mass of cyclohexanone oxime, a good extraction effect of cyclohexanone oxime (≥ extraction yield 99%) can be achieved. In addition, since the secondary oil phase is mainly toluene, it can also continue to be used as an extractant for recycling.

[0024] In a preferred embodiment of the present invention, the mass of toluene used in the first extraction is reduced to 0.4-0.8 times of the original mass, and the mass of toluene used in the second extraction is increased to 1.1-1.3 times of the original mass.

[0025] The inventor found that by reducing the mass of toluene used in the primary extraction and increasing the mass of toluene used in the secondary extraction on the basis of the original ratio, the extraction effect of cyclohexanone oxime in the secondary extraction and the mass proportion of cyclohexanone oxime in the toluene oxime solution can be greatly improved (the mass proportion of cyclohexanone oxime in the toluene oxime solution is increased from the original 10-25wt% to 35-50wt%), therefore, the overall cyclohexanone oxime extraction recovery effect is not affected, but the toluene consumption can be reduced (the toluene saving is not less than 10wt%), and the total toluene consumption can be less than 3 times the mass of cyclohexanone oxime, thereby saving steam and reducing energy consumption. For example, the mass of toluene used in the primary extraction can be any value of 0.4 times, 0.5 times, 0.6 times, 0.7 times, 0.8 times, etc., and the mass of toluene used in the secondary extraction can be any value of 1.1 times, 1.15 times, 1.2 times, 1.25 times, 1.3 times, etc., without special restrictions. In addition, it should be noted that if the mass of toluene extracted once is less than 0.4 times of the original mass, it will be detrimental to the final extraction effect of cyclohexanone oxime.

[0026] In a preferred embodiment of the present invention, the secondary extraction is a countercurrent extraction. The countercurrent extraction can ensure that the primary aqueous phase is in full contact with toluene, improve the extraction effect of cyclohexanone oxime in the primary aqueous phase, and reduce the loss of cyclohexanone oxime in the secondary aqueous phase.

[0027] In a preferred embodiment of the present invention, the conditions for the primary extraction and / or secondary extraction are: temperature of 45-55° C. and pressure of normal pressure.

[0028] Reference Figure 1 On the other hand, an embodiment of the present invention provides a system applied to any of the above-mentioned technical solutions, comprising a heat exchanger 6, an extraction tank 5, a first pump 9, an extraction tower 7, an extraction receiving tank 8, and a second pump 10 connected in sequence, the feed end of the heat exchanger 6 is used for feeding toluene 1 and cyclohexanone oxime aqueous solution 2, the discharge end of the heat exchanger 6 is connected to the middle of the extraction tank 5, the primary oil phase discharge end of the extraction tank 5 is connected to the desalination and distillation purification system, the primary water phase discharge end at the bottom of the extraction tank 5 is connected to one end of the first pump 9, the other end of the first pump 9 is connected to one end of the top of the extraction tower 7, the other end of the top of the extraction tower 7 is connected to the top of the extraction receiving tank 8 as the discharge end of the secondary oil phase, the bottom of the extraction receiving tank 8 is connected to one end of the second pump 10, the other end of the second pump 10 is connected to the feed end of the heat exchanger 6, the secondary water phase discharge end at the bottom of the extraction tower 7 is connected to the wastewater treatment system, and the bottom of the extraction tower 7 is also provided with a toluene feed end.

[0029] Example 1

[0030] A process for extracting and purifying cyclohexanone oxime, referring to Figure 1 The system shown comprises the following steps:

[0031] S1, toluene 1 and 100t cyclohexanone oxime aqueous solution 2 (cyclohexanone oxime accounts for 40% by mass) are mixed at a mass ratio of 0.8:1, cooled by a heat exchanger 6, and enter an extraction tank 5 for primary extraction (extraction temperature is 50° C., extraction pressure is normal pressure), to obtain a primary oil phase and a primary water phase, the upper primary oil phase is washed with water to remove salt, and then distilled and purified to recover the cyclohexanone oxime therein;

[0032] S2, the lower primary aqueous phase is pressurized by the first pump 9 and sent to the top of the extraction tower 7, toluene 1 enters from the bottom of the extraction tower 7, and the primary aqueous phase is subjected to secondary countercurrent extraction (the extraction temperature is 50° C., and the extraction pressure is normal pressure) to obtain a secondary oil phase and a secondary aqueous phase 4, the secondary oil phase enters the extraction receiving tank 8 from the top of the extraction tower 7, is pressurized by the second pump 10 and circulated to the primary extraction process (returning to the heat exchanger 6), and cyclohexanone oxime in the secondary oil phase is recovered, and the secondary aqueous phase 4 enters the wastewater treatment system from the bottom of the extraction tower 7;

[0033] The mass ratio of toluene 1 used in the primary extraction to toluene 1 used in the secondary extraction is 2:1.

[0034] The system applied to the above process includes a heat exchanger 6, an extraction tank 5, a first pump 9, an extraction tower 7, an extraction receiving tank 8, and a second pump 10 connected in sequence. The feed end of the heat exchanger 6 is used for feeding toluene 1 and a cyclohexanone oxime aqueous solution 2. The discharge end of the heat exchanger 6 is connected to the middle of the extraction tank 5. The primary oil phase discharge end of the extraction tank 5 is connected to a desalination and distillation purification system. The primary water phase discharge end at the bottom of the extraction tank 5 is connected to one end of the first pump 9, and the other end of the first pump 9 is connected to one end of the top of the extraction tower 7. The other end of the top of the extraction tower 7 is connected to the top of the extraction receiving tank 8 as the discharge end of the secondary oil phase. The bottom of the extraction receiving tank 8 is connected to one end of the second pump 10, and the other end of the second pump 10 is connected to the feed end of the heat exchanger 6. The secondary water phase discharge end at the bottom of the extraction tower 7 is connected to a wastewater treatment system. The bottom of the extraction tower 7 is also provided with a toluene feed end.

[0035] Example 2

[0036] The difference between this embodiment and embodiment 1 is that the amount of toluene used is different, the mass of toluene used in the primary extraction is reduced to 0.8 times of the original mass, and the mass of toluene used in the secondary extraction is increased to 1.1 times of the original mass, that is, the mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 16:11. The other steps remain unchanged.

[0037] Example 3

[0038] The difference between this embodiment and embodiment 1 is that the amount of toluene used is different, the mass of toluene used in the primary extraction is reduced to 0.625 times of the original mass, and the mass of toluene used in the secondary extraction is increased to 1.25 times of the original mass, that is, the mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 1:1. The other steps remain unchanged.

[0039] Example 4

[0040] The difference between this embodiment and embodiment 1 is that the amount of toluene used is different, the mass of toluene used in the primary extraction is reduced to 0.4 times of the original mass, and the mass of toluene used in the secondary extraction is increased to 1.3 times of the original mass, that is, the mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 8:13. The other steps remain unchanged.

[0041] It has been determined that the extraction yields of the same mass of cyclohexanone oxime aqueous solution in Examples 1-4 can all reach more than 99%, and Examples 2-4 can reduce the amount of toluene used in the first extraction and increase the amount of toluene used in the second extraction, thereby reducing the amount of toluene used (Examples 2-4 reduce by 10%, 16.7%, and 30% respectively compared with Example 1) and loss, effectively saving the steam required for recovering toluene, increasing the operating load of the extraction system, and improving economic benefits.

[0042] Comparative Example 1

[0043] The difference between this comparative example and Example 1 is that the amount of toluene used is different, the mass of toluene used in the first extraction is increased by 1.1 times, and the mass of toluene used in the second extraction is reduced by 0.8 times, that is, the mass ratio of toluene used in the first extraction to toluene used in the second extraction is 2.75:1. The other steps remain unchanged.

[0044] It was determined that the extraction yield of the same mass of cyclohexanone oxime aqueous solution in Comparative Example 1 was 98%, which was lower than that in Example 1. This was attributed to the limited improvement in the recovery effect of cyclohexanone oxime by the first extraction, and the increase in the loss of cyclohexanone oxime in the secondary aqueous phase, so the overall extraction effect of cyclohexanone oxime was slightly reduced.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 1 is that the amount of toluene used is different, the mass of toluene used in the first extraction is reduced to 0.3 times the original mass, and the mass of toluene used in the second extraction is increased to 1.3 times the original mass, that is, the mass ratio of toluene used in the first extraction to toluene used in the second extraction is 6:13. The other steps remain unchanged.

[0047] It was determined that the extraction yield of the same mass of cyclohexanone oxime aqueous solution in Comparative Example 2 was 96%. This was attributed to the fact that the amount of toluene used in the first extraction was too small, which significantly increased the difficulty of the second extraction, resulting in an increase in the amount of residual cyclohexanone oxime in the secondary aqueous phase, and thus the overall cyclohexanone oxime extraction effect decreased.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for extracting and purifying cyclohexanone oxime, characterized in that: The following steps are involved: S1, extracting the cyclohexanone oxime aqueous solution once with toluene to obtain an oil phase and an aqueous phase, washing the oil phase with water to remove salt and then distilling and purifying it to recover the cyclohexanone oxime therein; S2, extracting the primary aqueous phase with toluene for a second time to obtain a secondary oil phase and a secondary aqueous phase, and then recycling the secondary oil phase to the primary extraction step to recover cyclohexanone oxime in the secondary oil phase; The mass ratio of toluene used in the primary extraction to toluene used in the secondary extraction is 2:

1.

2. The extraction and purification process of cyclohexanone oxime according to claim 1, characterized in that: The mass of toluene used in the primary extraction is reduced to 0.4-0.8 times of the original mass, and the mass of toluene used in the secondary extraction is increased to 1.1-1.3 times of the original mass.

3. The extraction and purification process of cyclohexanone oxime according to claim 1, characterized in that: The secondary extraction is countercurrent extraction.

4. The extraction and purification process of cyclohexanone oxime according to claim 1, characterized in that: The conditions of the primary extraction and / or the secondary extraction are: temperature of 45-55° C. and pressure of normal pressure.

5. A system for use in the process according to any one of claims 1 to 4, characterized in that: The invention comprises a heat exchanger, an extraction tank, a first pump, an extraction tower, an extraction receiving tank and a second pump which are connected in sequence. The feed end of the heat exchanger is used for feeding toluene and cyclohexanone oxime aqueous solution. The discharge end of the heat exchanger is connected to the middle of the extraction tank. The primary oil phase discharge end of the extraction tank is connected to a desalination and distillation purification system. The primary water phase discharge end at the bottom of the extraction tank is connected to one end of the first pump. The other end of the first pump is connected to one end of the top of the extraction tower. The other end of the top of the extraction tower is connected to the top of the extraction receiving tank as a discharge end of the secondary oil phase. The bottom of the extraction receiving tank is connected to one end of the second pump. The other end of the second pump is connected to the feed end of the heat exchanger. The secondary water phase discharge end at the bottom of the extraction tower is connected to a wastewater treatment system. A toluene feed end is also provided at the bottom of the extraction tower.

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